[Android] Add slack to allow refresh after overscrolling

content/browser/android/edge_effect.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/android/edge_effect.h"
 
 #include "cc/layers/layer.h"
 #include "cc/layers/ui_resource_layer.h"
 #include "content/browser/android/animation_utils.h"
 #include "ui/android/resources/resource_manager.h"
@@ skipping 287 matching lines @@
         break;
     }
   }
 
   if (state_ == STATE_RECEDE && glow_scale_y_ <= 0 && edge_scale_y_ <= 0)
     Finish();
 
   return !IsFinished();
 }
 
+float EdgeEffect::GetAlpha() const {
+  return IsFinished() ? 0.f : std::max(glow_alpha_, edge_alpha_);
+}
+
 void EdgeEffect::ApplyToLayers(const gfx::SizeF& size,
                                const gfx::Transform& transform) {
   if (IsFinished())
     return;
 
   // An empty window size, while meaningless, is also relatively harmless, and
   // will simply prevent any drawing of the layers.
   if (size.IsEmpty()) {
     edge_->Disable();
     glow_->Disable();
@@ skipping 23 matching lines @@
 // static
 void EdgeEffect::PreloadResources(ui::ResourceManager* resource_manager) {
   DCHECK(resource_manager);
   resource_manager->PreloadResource(ui::ANDROID_RESOURCE_TYPE_SYSTEM,
                                     kEdgeResourceId);
   resource_manager->PreloadResource(ui::ANDROID_RESOURCE_TYPE_SYSTEM,
                                     kGlowResourceId);
 }
 
 }  // namespace content